Internal combustion engines combust a fuel and air mixture within cylinders driving pistons to produce drive torque. The engine drives a transmission through a coupling device. In the case of an automatic transmission, the coupling device includes a torque converter. The transmission transfers the drive torque to a driveline through one of a plurality of gear ratios. The transmission shifts between gear ratios based on a shift schedule and vehicle operating conditions.
The transmission typically includes a plurality of clutches that are selectively engaged to establish a desired gear ratio. When shifting between gear ratios, clutch-to-clutch shifts occur. More specifically, at least one clutch is disengaged (i.e., off-going clutch) while another clutch is concurrently engaged (i.e., on-coming clutch). Control of the clutch-to-clutch shift is based on an estimated engine torque (TEST). TEST is determined using a torque estimating calculation that is based on engine operating conditions. However, TEST is not always sufficiently accurate to provide the desired clutch-to-clutch shift quality. More specifically, the transmission is sensitive to error in TEST, which reduces the shift quality of the transmission.